This re-submission for a competitive renewal aims towards continuing to develop and verify MR oximetry techniques for noninvasive assessment of congenital heart disease. The proposed goal will be approached in three stages. First, they propose to perform an initial clinical study to establish that MR oximetry, with straightforward modifications, can already answer significant clinical questions for cooperative patients who have heart defects with stable hemodynamics, typically atrial septal defects. The second stage will address the problem of performing MR measurements in cooperative patients with adverse flow characteristics such as high flow jets. The third stage extends the application of the previously developed techniques to infants and children where the anatomy is smaller, heart rates are faster, and the ability to cooperate is reduced. At each stage, technically more challenging advances in the measurement process will be required and developed progressively. The results of this investigation will significantly enhance the management of children and young adults with congenital heart disease while extending the general utility of MR oximetry.